Sirisena to be Sworn in as Sri Lanka President Friday

Maithripala Sirisena will be sworn in as Sri Lanka's new president Friday after the strongman incumbent conceded defeat in a bitterly fought election, brought down by charges of corruption and growing authoritarianism.

A top aide to Mahinda Rajapakse said the outgoing president accepted the decision of voters who turned out in force on Thursday, in a remarkable turnaround for a leader who had appeared certain of victory when he called snap polls in November.

"The president concedes defeat and will ensure a smooth transition of power, bowing to the wishes of the people," presidential press secretary Vijayananda Herath told Agence France Presse, adding he had already vacated his main official residence in a symbolic gesture of defeat.

There was no immediate comment from Sirisena, who was expected to travel to Colombo after spending the night at his home in Polonnaruwa, east of the capital.

A spokesman for the opposition said the former health minister, who united a fractured opposition to pull off an unlikely victory, would be sworn in later Friday.

"The swearing in will be at 6:00 pm (1230 GMT) today at Independence Square," said Saman Athaudahetti.

- Unassailable lead - 

Official sources said Sirisena had an unassailable lead in results announced so far.

With nearly a third of results officially declared, Sirisena has 52.49 percent of the vote and Rajapakse 46.21 percent.

Sirisena was a relative unknown until he became the main opposition candidate, but his decision to run triggered a slew of defections and became a rallying point for disaffection with Rajapakse and his powerful family.

Rajapakse won a landslide election victory in 2010, but critics say he has failed to bring about reconciliation in the years that followed his crushing victory over the Tamil Tiger separatist group in 2009.

Herath said Rajapakse had conceded defeat during a meeting with Ranil Wickremesinghe, who leads the opposition in parliament and who Sirisena has said would be appointed as his prime minister.

Opposition lawmaker Harsha de Silva said transitional arrangements were being discussed with Rajapakse, and that Wickremesinghe had "guaranteed him and his family security".

U.S. Secretary of State John Kerry welcomed Rajapakse's early concession and said he looked forward to working with the new leader.

"I commend President Rajapaksa for accepting the results of the election in the proud tradition of peaceful and orderly transfers of power in Sri Lanka," he said in a statement.

Indian Prime Minister Narendra Modi said he had spoken to Sirisena to congratulate him.

Sirisena has promised to reform the executive presidency, abolishing many of the executive powers that Rajapakse had awarded himself during his second term in office.

Opposition figures have accused the president of skimming large amounts of money from infrastructure projects funded through expensive foreign loans, often from China, his strongest foreign political and economic ally.

He is also accused of undermining the independence of the judiciary and has packed the government with relatives, sparking resentment even within his own party.

Rajapakse had seemed assured of victory when he called snap polls in November seeking an unprecedented third term, five years after crushing a violent separatist rebellion that had traumatised the country for decades.

But he has become unpopular in recent years, dogged by accusations of increasing authoritarianism and corruption, and a failure to reach out to minority Tamils after a decades-long civil war.

Sirisena's surprise decision to defect from the government and stand against him galvanised disparate opposition groups.

Despite sporadic campaign violence including the death of one opposition party worker, the vote passed off largely peacefully, although there were some reports of intimidation in Tamil areas.

The president had come under international pressure after opposition reports that he was mobilising the military, with Kerry this week urging him to ensure the election was peaceful and credible.

The polls came days before a visit to the island by Pope Francis which some Catholic leaders had said should be cancelled in the event of violence.

- Tamil kingmakers - 

Election monitors said large numbers of people had voted in the heavily militarised former war zones of the north and east, whose largely Tamil population had boycotted previous national elections.

The head of the Campaign for Free and Fair Elections Keerthi Thennakoon said before Rajapakse's concession that the high participation could favour the opposition.

Tamils are Sri Lanka's largest minority, accounting for 13 percent of the population, and were in a position to decide the election if the majority Sinhalese vote split between Rajapakse and his main opponent.

Rajapakse had promised a judicial inquiry into allegations troops killed 40,000 Tamil civilians at the end of the civil war, although he had refused to cooperate with a UN-mandated investigation.